1. Field of the Invention
The subject invention relates to a laminated pole piece assembly for use in an electric motor.
2. Description of Related Art
Laminated pole piece assemblies for electric motors are well known in the art. As shown in FIG. 1, laminated pole piece assemblies 10 are typically formed of a plurality of lamina 12 that are stacked onto each other. U.S. Pat. No. 2,512,351 also illustrates a typical laminated pole piece assembly. The stacked plurality of lamina can be held together by brazing, such as discussed in the ""351 patent. Many of the laminated pole piece assemblies 10 also include a post 14 extending through a central portion thereof. U.S. Pat. Nos. 922,760 and 1,991,092 also illustrate such a structure. As shown in U.S. Pat. No. 2,236,291, the laminated pole piece assemblies are often bolted to a stator of the electric motor.
It is well known in the metal lamination industry that drilling into the laminated pole piece assemblies 10 creates a host of problems. In particular, the lamina 12 have a tendency to separate from each other during the drilling process. In addition, a series of burs 16 are typically created at an outer surface of the lamina 12, see FIG. 1. Also, a portion of each of the lamina 12 is placed into integral contact with an adjacent lamina 12, which is known in the industry as xe2x80x9cwipingxe2x80x9d, again see FIG. 1. This integral contact creates an undesirable short circuit at the drilling interface thereby concentrating the electrical flux pattern and increasing the temperature at this point. This short circuit in turn reduces the electrical efficiency of the electric motor.
Accordingly, it would be desirable to develop a laminated pole piece assembly that can be bolted to a stator of an electric motor without drilling into the stack of interlocked lamina.
A pole piece assembly for an electric motor comprising a plurality of lamina stacked onto each other defining a first set of stacked lamina and a second set of stacked lamina. Each of the lamina of the first and second sets of stacked lamina include a hole disposed therein with the holes being aligned with each other to define an internal cavity. A post is disposed within the cavity with the post having an outer surface and at least one bore disposed therein. The pole piece assembly is characterized by each of the lamina of the second set of stacked lamina further including a first notch disposed therein with the first notch mating with the hole. The first notches of the second set of stacked lamina are aligned with each other to define a first passageway into the internal cavity with the bore of the post being aligned with the first passageway to expose the bore.
Accordingly, the subject invention resolves the problems associated with the prior art by incorporating a notch in the lamina surrounding the bore to define a passageway to the bore. As such, a bolt can be tapped into the bore of the post through the passageway to mount the pole piece assembly to a stator without drilling through the stacked lamina. Preferably, a counter bore configuration is created.